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PHP and MySQL

A2 Project Starter Guide

http://xkcd.com/327/

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Contents About this guide ......................................................................................................................... 4

A quick word about software................................................................................................. 4

What is PHP? .............................................................................................................................. 5

How do I set up a server? .......................................................................................................... 6

Uh oh…why isn’t it working? ................................................................................................. 6

How do I write PHP programs? .................................................................................................. 7

Where do I put my programs? ............................................................................................... 7

How do I write a program? .................................................................................................... 8

What you should have understood so far ............................................................................. 8

PHP mixed with HTML ............................................................................................................... 9

Things to watch out for .......................................................................................................... 9

Concatenating variables ....................................................................................................... 10

PHP and HTML exercise ....................................................................................................... 11

Basic PHP .................................................................................................................................. 12

Assignment ....................................................................................................................... 12

Selection ........................................................................................................................... 12

While loop ........................................................................................................................ 12

For loop ............................................................................................................................ 12

Do-while loop ................................................................................................................... 12

Operators ......................................................................................................................... 12

PHP exercises ....................................................................................................................... 13

User input................................................................................................................................. 14

Important parts to note ................................................................................................... 14

What happens when I press the button? ............................................................................ 14

Mini Project 1 – Love Calculator .......................................................................................... 16

Input page – index.php .................................................................................................... 16

Processing/output page – calculate.php ......................................................................... 16

Sending information via the URL ......................................................................................... 17

Using $_GET data example .................................................................................................. 17

More PHP exercises ............................................................................................................. 19

PHP and MySQL – Database Integration.................................................................................. 21

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Creating a MySQL user account ........................................................................................... 21

Creating a database ............................................................................................................. 22

Creating a table .................................................................................................................... 22

Connecting PHP with MySQL ................................................................................................... 24

Connecting to the database ................................................................................................. 24

Mini Project 2 – Shoutbox .................................................................................................... 25

Displaying the input form ................................................................................................ 25

Processing the data .......................................................................................................... 25

Putting data in to the database ........................................................................................... 26

What’s going on here? ..................................................................................................... 27

Getting data out of the database ........................................................................................ 28

A general example ........................................................................................................... 28

How to display your shouts ............................................................................................. 29

Improvements to the shoutbox ........................................................................................... 30

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About this guide This guide is written for A2 Computing students, and as such it

assumes you have some basic procedural programming knowledge in

a language other than PHP.

I also assume you already know how to use basic HTML and CSS. If

you don’t, have a look at my HTML, CSS, Javascript and jQuery booklet

first.

PHP stands for PHP: Hypertext Preprocessor. The name is recursive - I hope you get the joke

If you would like to get in touch, please find me on Twitter @codeboom or visit

http://codeboom.wordpress.com

Please feel free to copy, adapt and distribute as described under this Creative Commons

license http://creativecommons.org/licenses/by-nc-sa/3.0/

A quick word about software

You will need to use a text editor to type in all of the code in this document. You could use

something really basic like Notepad (or TextEdit on Mac) but it’s probably worth

downloading a proper code editor, they are invaluable. I like these ones on Windows:

- Notepad++ - free

- PSPad – free

- Dreamweaver (code view) – not free, and a bit overkill, but if you already own it then

great!

You will also need an internet browser. I realise that in most schools you don’t have a choice

and you are probably stuck with Internet Explorer, but if your neighbourhood techies are

rather lovely it’s worth asking them to install Chrome just for the lovely JavaScript

debugging facilities.

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What is PHP?

PHP is a scripting language primarily used to make interactive web pages. It is a server side

language which means it does its processing on a server, a bit like this:

So…the user only ever sees HTML pages. They cannot see the PHP code!

What is PHP good at? What is PHP bad at?

It is easy to connect your website to a database in order to store data

In order for anything to update on the page a request for a new page must be sent to the server (e.g. by clicking a link or submitting a form)

It has lots of useful built in functions you can use to help you, and good docs on php.net

You have to run a server (or pay for hosting with PHP) or your code will not run

You can use HTML to make your interface – easy!

Not really PHP’s fault, but you still have to contend with designing for multiple browsers.

It can be used procedurally or in Object Oriented style

The Object Oriented support in PHP is relatively new and some people don’t like it.

Server running PHP I clicked a link to

page.php

User

Request sent to server

Server processes

PHP code…

…and produces a

HTML page

…the HTML is

sent back to the

user

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How do I set up a server? Happily, there are some nice people on the internet at http://apachefriends.org who have

made things very easy! They offer a package called XAMPP which contains everything we

need in one easily installable package. It even works on OSX and Linux (although my

instructions were written using Windows).

XAMPP contains…

Apache – a web server to send out the pages

PHP – interpreter for the PHP language

MySQL – database software

Some other stuff we don’t really need to care about

1. Download either XAMPP (the full Monty) or XAMPP USB Lite if you want the small

version so that you can install it on a USB stick or other portable hard drive.

2. Open the installer and follow the instructions. It is best to install XAMPP in a

permanent location rather than on the desktop.

3. Once the installer has finished, find the xampp-control.exe (you might want to make

a shortcut to this) and run it. Click on “Start” next to the Apache and MySQL options

and make sure they go green and say “Running”. You can now close the window.

Uh oh…why isn’t it working?

Obviously network environments vary and school networks are often frustratingly locked

down. Apache is a web server which operates on port 80, and MySQL uses port 3306. If you

have Skype or some other communication program running, this often uses port 80

meaning Apache won’t run – so close it and try again. For other problems consult

http://apachefriends.org or your friendly network technician (bring tea?)

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How do I write PHP programs? First, let’s test whether your server is actually working. Assuming you managed to start

Apache and MySQL on the previous page, open up your browser and type in

http://localhost/ (or if you’re feeling techy, http://127.0.0.1 which means the same)

You should see the XAMPP test page if it’s working correctly, if not see the bottom of the

previous page for troubleshooting advice.

Where do I put my programs?

When we write PHP programs we need to save them in a special folder on the server called

htdocs. This is the web root – it’s where the server looks for pages. Find it by navigating to

the place where your XAMPP was installed and looking for the htdocs folder, here is mine:

1. Make a subfolder inside the htdocs

folder called myapp

2. Open up a blank file in a text editor

of your choice (I recommend

Notepad++) and save your file as

index.php inside the myapp folder

Be careful that you don’t

accidentally save the file as

index.php.txt which can easily

happen in Notepad if you don’t change the

‘Save as type’ dropdown to “*.* All files”. In

Notepad++, just change the ‘Save as type’ to

PHP and that should do the job nicely.

You might be wondering why we have called our page index.php ? Apache

(the web server) always looks for a page called index first – this is the

home page of any site or app we may make. Other files can just be saved

as filename.php and will work just as well.

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How do I write a program?

Now we need to write some PHP code! PHP is always written within PHP tags which look

like this:

<?php ?>

Here is my program – I’m sure you can tell that the green part is a comment.

Now run the program by visiting this address

in your browser:

http://localhost/myapp

Congratulations, you are now a PHP programmer!

If you did not call your folder myapp, your address will be

http://localhost/yourfoldername - replace yourfoldername with the name you

called your folder.

What you should have understood so far

When you want to work on PHP code you need to start Apache/MySQL on the

XAMPP control panel

Save all of your PHP documents into the htdocs folder with the file extension .php

PHP files can be inside subfolders of htdocs

Run your PHP file by browsing to http://localhost/foldername

The default page (home page) of each folder is index.php

If you want to view a page with a different name, open

http://localhost/foldername/pagename.php

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PHP mixed with HTML As I mentioned at the start, to create the interface for PHP programs you can use HTML.

This means we can combine PHP and HTML code in our program:

Document contains both PHP PHP statements evaluated Final output is

and HTML code to produce HTML code only HTML code

You can easily tell which parts are HTML code and which are PHP code because PHP code

always has to be inside the PHP tags <?php and ?>

Things to watch out for

1. If you want to output something from a PHP section, you have to print it as a string

Correct Will cause a syntax error

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2. Sometimes you may want to put some HTML code inside a PHP section. This is fine,

but you must treat it as if it were just another string to be printed:

This will cause a syntax error because the

HTML code is inside a PHP section

This will work as you have treated the HTML

tags as strings

You can also do this

Concatenating variables

You can concatenate variables into your output using the concatenation operator which is a

dot in PHP:

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PHP and HTML exercise

Test your understanding of the differences between HTML and PHP

HTML PHP

Is a ______________ language.

Is a ____________ language.

Tells the __________ how to __________ the items on the page.

Processes the code on the __________ and then sends the result back to the browser.

Each tag begins with a ___ and ends with a ___

Most lines end with a ___

The bit within a tag such as “color=blue” is known as an ____________

A line of code is known as a ____________

Can temporarily store data in a _________

Can be used to connect to a ______________

Mark-up Statement <

RAM Scripting Display

Variable Server >

Internet ; Database

Browser Code Attribute

Score: / 12

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Basic PHP You will already be familiar with another programming language from your AS work. Here is

a quick reference of the basic statement syntax for PHP

Assignment Variable names in PHP have a dollar sign ($) in front of them, e.g.

$name = “Bob”;

$age = 10;

The assignment operator is a single equals =

Selection if ( condition ){

// statements here

}

elseif ( condition ) {

// statements here

}

else {

// statements here

}

While loop

while( condition ){

// statements here

}

For loop

for( $i = 0; $i < 5; $i++ ){

// statements here

}

$i = 0 Create a variable $i and set its starting value to 0 $i < 5 Condition to test. While this condition remains true, the loop will execute $i++ Increment (add one) to $i

Do-while loop

do {

// statements

while ( condition );

Operators The comparison operator is a double equals == Logical ‘and’ operator is &&

Logical ‘or’ operator is || (pipe is to the left of Z on a Windows keyboard) The concatenation operator is a dot .

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PHP exercises

Printing - HTML and PHP

1. Write the phrase “Hello World” as HTML, with a line break afterwards

2. Print the phrase “Strawberry Jam” using a php print statement

3. Make “Hello World” bold

4. Make “Strawberry Jam” bold

Variables

1. Make a variable called firstname and assign it the value of your own first name

2. Make a variable called age and assign it the value of your age

3. Make a variable called blueeyes and assign it to either true or false

Printing with variables

1. Print a line that says “Hello <name>, nice to meet you!” where <name> is the value

of your variable called firstname

2. On the next line, print a line that says “<name> is <age> years old.” and make the

whole line italic.

If statements

1. Create an if statement that will print “<name> has blue eyes” if the variable

blueeyes is true.

2. Add a part to your if statement that will print “Eye colour unknown” if the variable

blueeyes is not true

Calculations

1. Create a variable called badgers. Initialise it to 10 badgers.

2. Create a variable called mushrooms. There are currently 100 mushrooms.

3. Print a statement detailing how many badgers and mushrooms there are currently.

4. Using a simple division calculation, print out a statement about how many

mushrooms each badger will get, assuming the mushrooms are evenly divided. How

many mushrooms are left over?

5. Create a variable called babybadgers. Each badger couple has one child. Using a

simple calculation work out how many extra badgers there are now and store this

value inside babybadgers.

6. Six mushrooms are trampled and 31 mushrooms are eaten by a snake. Write code to

change the value of the variable mushrooms to reflect this.

7. Write a statement to show how many mushrooms each badger gets now that the

new baby badgers are also eating the mushrooms.

8. If badgers do not get more than 5 mushrooms each, they will be hungry. Using an if

statement, decide whether the badgers are too hungry or are just right.

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User input This is probably slightly more complex than in the language you have already studied,

because of the fact that PHP is a server side language. Here’s how it works in PHP:

User sees input page User presses button Data received by PHP

and types in data to submit data page and processed

This is some HTML code for a basic input page

<form method=”post” action=”page2.php”>

<input type=”text” name=”username” value=”Text goes here”>

<input type=”submit” value=”Send Data”>

</form>

It will look something like this:

Important parts to note

The action of the form is the PHP page which will do the processing of this

information. (You can even tell the page to send the data to itself!)

You should have a submit button or you won’t be able to send the data

Be careful what you name your fields. In my example, the text box is called

username. You will use these names on the processing page.

Beware if you are copying the code from this document – Word adds styled quote

characters which will cause an error!

What happens when I press the button?

Because we have selected the method “post”, PHP takes all of the data that was typed in

and puts it in an array called $_POST

$_POST

Array key Value

‘username’ (What you typed in the box)

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So on our processing page (in this case page2.php) we can put the following code to see

what the user typed in the box:

<?php

print $_POST[‘username’];

?>

We often want to see everything that was $_POST –ed to the next page for debugging

purposes. You can print the whole $_POST array on the processing page like this:

<?php

print “<pre>”;

print_r( $_POST );

print “</pre>”;

?>

This would produce the following output if I typed in awesomezz in the box:

The $_POST array is global so you can use it however you like on this page:

You can add more fields to your input page, they will be referenced in the $_POST array

with the name attribute as their key, e.g. whatever is typed into this field…

<input type=”text” name=”batman”>

…will become the variable

$_POST[‘batman’];

…on the processing page. (You can obviously decide on sensible variable names yourself!)

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Mini Project 1 – Love Calculator

Create a new subfolder inside htdocs called lovecalc

Input page – index.php

Create an input form with a space for the user to input two

names and a submit button.

Make sure you give the text boxes sensible names

Make sure you set the form action to be calculate.php

Processing/output page – calculate.php

Processing

Create a page which will receive the $_POST data and use it to calculate the two people’s

compatibility. The secret love algorithm is as follows:

Find the number of letters in name1 and name2 – look up the strlen() function

on php.net to find out how to do this!

Add the two lengths together and save the result inside a variable

If name 1 is longer than name 2, take off 5 from the total, else add 3

Multiply the total by 42 and then divide by 100

If the total is greater than 10, change the total to

equal exactly 10, else round it to zero decimal places –

look up the round() function on php.net

Output

Print out the two names (remember they are stored in the

$_POST array) and the compatibility score you just

calculated.

If you like, you can also use a loop to print out that number of

heart images. You could include a meta refresh to go back to

the first page too:

print '<meta http-equiv="refresh" content="5; url=index.php">';

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Sending information via the URL

Now we know how to get the user to input information using a form. However, sometimes

we need to send information from one page to the next without the user having to type

something in.

We can send information from one page to another via the URL – this is called $_GET data

because it is passed to the next page in an array called $_GET.

Here is a basic example:

Put the following HTML code on your first page – index.php

<a href=”page2.php?month=September”>Next page</a>

Put the following code on page2.php

<?php

print $_GET[‘month’];

?>

The name of the variable in bold will be the same as the name you gave it in the link

You can add more than one item to the link by separating it with & like this:

page2.php?month=September&year=2011&day=19

<?php

print $_GET[‘month’];

print $_GET[‘year’];

print $_GET[‘day’];

?>

Using $_GET data example

Have you ever searched for products on a shopping website? When there are lots of results

they will often appear on several pages, and you can press next and previous to skip through

the pages. This can be done in PHP using $_GET data!

See if you can understand what the code on the next page does, and add

suitable comments (the comment escape is // in PHP) to explain what is

happening:

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<?php

if(empty($_GET)){

$_GET['page']=1;

}

$previous = $_GET['page'] - 1;

$next = $_GET['page'] + 1;

print "This is page number ". $_GET['page'] . "<br>";

if($_GET['page'] != 1){

print "<a

href=\"paginator.php?page=$previous\">Previous</a> ";

}

if($_GET['page'] != 5){

print "<a href=\"paginator.php?page=$next\">Next</a>";

}

?>

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More PHP exercises

Exercise 1

Can you take the following instructions known as pseudo code and turn them into a proper

PHP program?

Set a counter variable to be equal to 1

Make a ‘for’ loop that executes 5 times (using the counter

variable)

Print a font tag with the counter variable as the font

size

Print out “Hello”

End the font tag

Print out a line break

End the loop

This should produce something that looks a bit like this:

Hello

Hello

Hello

Hello

Hello

Exercise 2

Write a program that contains a variable called $rows. The program should use a loop (for

or while) to print out a table with $rows numbers of rows. The table always has 1 column.

e.g. $rows = 2;

Row

Row

The HTML code is below to help you

<table> // This gets printed out once

// The next line goes within the loop

<tr> <td>Row</td> </tr> // This gets printed out $rows

times

</table> // This gets printed out once

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Exercise 3

Alter your code from Event 2 to make it print out the correct row number inside each table

cell

Row 1

Row 2

Exercise 4

Write a program to automatically print out a one column table with alternating cell

background colours. You should be able to vary the amount of rows in a loop (see part 1) –

this will help you!

1

2

3

4

5

This is the HTML code to help you: <table>

<tr><td bgcolor=”white”>Cell</td></tr> // Print this $rows

times

<tr><td bgcolor=”grey”>Cell</td></tr>

….etc

</table>

Exercise 5

Anyone who can manage this is a true Programming God or Goddess!

Can you make a checkerboard effect?

R1 C1 R1 C2 R1 C3 R1 C4 R1 C5

R2 C1 R2 C2 R2 C3 R2 C4 R2 C5

Hint: If you want to decide whether a row is odd or even, you can use modulus:

$result = $counter % 2;

This divides $counter by 2 and puts the value of the remainder in the variable

$result – it will either be 0 (even) or 1 (odd)

So then you can do a check: if $result is 0 (print white) else (print grey)

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PHP and MySQL – Database Integration

Creating a MySQL user account

Your installation of XAMPP comes with MySQL which allows you to create databases. There

is a useful interface to administrate your databases called phpmyadmin – you can get to it

by browsing to

http://localhost/phpmyadmin

This is the phpmyadmin

interface – you can see

some of the databases I

have already created in the

list on the left.

Some of the databases are

premade e.g.

information_schema – don’t

delete them or

phpmyadmin may go wrong

To create a user account for yourself so that you can connect to databases, click on

Privileges at the top and then click on Add a new user

Your installation of phpmyadmin might look slightly different to mine, but I’m

sure you can figure out how it works!

Choose a username.

Host should be localhost

Choose a password

Don’t click on generate

password!

Then scroll down and tick all of

the boxes (click on check all) to

make your user able to do

everything.

Then click the “Create User”

button

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Creating a database

Now that you have a user account, you need to create a database. Click on the Databases

tab at the top:

Type the name of your database in the box and click “Create”. You can ignore the Collation

drop down. I called mine shoutbox because it is going to be for the project we will do later.

Don’t use any spaces in your database name use underscores or camel/Pascal

case to distinguish between words.

You should see the name of your database appear in the list on the left. You can click on its

name to see it (there is nothing inside it yet).

Creating a table

When you have clicked on your database in the left hand side list you will be given an

opportunity to create a table.

Type the name of the table and the number of columns inside the boxes. I am going to call

my table shouts and I want 3 columns – again, this is for our mini project that is coming up.

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You will be asked to fill in the details for your table. Column is the field name, Type is the

data type of this field, Length/values is how long a space to reserve. You can set which field

is the primary key by selecting an option for it in the Index drop down.

Here is how I am going to fill in this form for my shouts table:

As you have probably figured out by now, I’m working up to showing you how to create a

basic project – a shoutbox! This is a bit like a very basic Facebook wall, with a box where a

user can write comments and the previous comments also displayed.

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Connecting PHP with MySQL

PHP is really good for making applications which are linked to a database. You will have

learnt about SQL and databases in your F453 module so now it is time to apply those

concepts.

There are two sets of functions in PHP which allow you to connect to the

database – mysql and mysqli. They are NOT interchangeable which means

you must pick one and stick to it. I recommend picking mysqli as this is the

new version – mysql is out of date, or to use the proper term it is deprecated.

I will be using the procedural style in the following examples, OO is available – see php.net

Connecting to the database

The easiest way to do this is to create a file and save it as connection.php. Your connection

file should have the following information inside it:

<?php

$link = mysqli_connect('localhost', 'my_user', 'my_password', 'my_db');

?>

Obviously, fill in your own MySQL user, password and database name!

Then, whenever you need to connect to the database in a program, use the line:

<?php require_once(“connection.php”); ?>

This will grab the contents of the connection.php file and insert it into the page so that you

can use the $link variable as the connection you’ve already set up.

Why do I need a separate file? Can’t I just put the connection line on the top

of each page? Well yes, you can. But imagine if you change your server

details – which will definitely happen if you are testing your site on XAMPP

and uploading to an online webserver later on. You’ll have to change the

details in every single page. If you put them in a connection file and require that

file wherever a connection is needed, you only need to change the details once in

the connection file instead of everywhere. Genius!

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Mini Project 2 – Shoutbox

We’ve actually already started this project, so if you have not already done so please start

from the “PHP and MySQL – Database Integration” section on page 21.

Create a subfolder called shoutbox inside htdocs, and inside there create a file called

index.php. Put the connection file you just created inside this folder as well.

Displaying the input form

We need a basic input form where the user can type in their shout, like this:

To make a larger box like the one above, you could use a <textarea>, the code looks like this:

<textarea name=”shout”></textarea>

If you can’t remember how to make the form, have a look on page 14 for some tips. You can

style the form to your liking using CSS if you want to make it look prettier.

Processing the data

When the user types their shout in the box and clicks the button, the code should send this

data to a processing page called send.php

This means that the form action inside index.php should be <form

action=”send.php”>

Create and save a file called send.php inside the shoutbox folder in htdocs

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Putting data in to the database

Assuming you have already included your connection file, this is the basic format for a query

// Create the query

$query = “INSERT INTO tablename(field1, field2, field3) VALUES

(‘value1’, ‘value2’, ‘value3’)”;

// Execute the query

$result = mysqli_query($link, $query);

You need to put in your own table name, field names and values. The values should be in

the same order as the field names, i.e. value1 will go into field1 etc.

This is the code I have inside my send.php page

Lines 1-13 are PHP code to insert the shout into the database. Lines 15-24 are HTML code

which provides a meta refresh – on line 17 the code specifies to wait 0 seconds and then go

to index.php. This means that once the page is done with inserting the data into the

database, it redirects quickly to the first page.

If you like the cartoon on the front page of this booklet, you may be worried about

validation and SQL injection – these are improvements you can make to the shoutbox, see

page 30 for details.

27

What’s going on here?

Let’s take a closer look at some of the PHP code in the processing page

This is some validation – I am checking that the shout they entered was not an empty string.

I could also have done it this way:

if( !empty($_POST[‘shout’]) ) { … }

This checks whether the variable $_POST[‘shout’] is not empty. (Don’t forget we can refer to

what the user typed in as $_POST[‘shout’] because it is passed to this page in the $_POST

array, and it has the index ‘shout’ because that was the name of our textarea on index.php)

This part looks a bit technical, but it isn’t. The first argument on line 8 is the database link

variable that we created in the connection.php file. The second argument is the query itself.

In the above code, on line 11 we are using concatenation to put the $_POST[‘shout’]

variable inside the query. If the amount of quotes messes with your head, try renaming the

variable (line 8) and then you can use its short name on line 9. It works exactly the same but

it’s a poor and inefficient way of coding and you should try to understand the concatenation

method above if you can.

The “or die” part means that if the query cannot be done for whatever reason, the page

should stop executing and give us a mysql error message so that we can debug it.

28

Getting data out of the database

Now we are back on the index page, our data has been inserted into the database, but we

can’t yet see the shouts displaying below the message box.

Go back and edit your index.php file, and after the code for the form add a PHP section

A general example

Here is a general example of how to write a SELECT query to get data from your database

// Write the query

$query = “SELECT fieldname FROM tablename”;

// Execute the query

$result = mysqli_query($link, $query);

// If anything was found, get the results

while($data = mysqli_fetch_assoc($result)){

print $data[‘fieldname’];

}

In this example, you specify which fields you would like from which table, when you write

the query.

In this example, the results are put one by one into an array called $data

$data = mysqli_fetch_assoc($result);

You can then reference each field by its name

e.g. if you had a field called username you could use...

print $data[‘username’];

...if you had a field called dateofbirth you could use

print $data[‘dateofbirth’];

29

How to display your shouts

Here is the code now in my index.php page

On lines 20-21 I do a query in exactly the same way as we discussed before – except that

this is a SELECT query to get data from the database, and not an INSERT query to put data in

the database.

Lines 24-27 are a loop which iterates through all of the rows of data returned by the query,

printing out the shout text and a HTML newline character (<br>).

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Improvements to the shoutbox

There are numerous ways you could improve your shoutbox code, here are some ideas for

you to work on, in order of difficulty!

Tidy up the presentation of your input form using CSS

Make the page display the time and date of the shout as well

Only show the top 5 most recent shouts

Print alternate shouts in a different colour (hint: use MOD or %)

Add another input box for the user’s name, save this in the database and display it

along with the shout

Make the user’s name persist in the box after they have submitted the form (hint:

try a hidden field in the form?)

Look up some PHP validation functions such as strip_tags() and stripslashes() on

php.net and try to use them to validate your input

Look up what SQL injection is and try to prevent it from being possible on your

shoutbox – try mysqli_real_escape_string() function on PHP.net

To come in future updates of the book:

- Session variables

- Creating a basic login system